The goal of this research project is to develop technologies that enable reproducible mRNA extraction from cerebrospinal fluid (CSF) for subsequent gene microarray analysis. In the series of studies proposed here, a "molecular fingerprint" will be created using CSF from: 1) pediatric cancer survivors with neurodevelopmental and cognitive impairments secondary to chemotherapy treatment and 2) subjects with age-related neurodegenerative disorders such as Alzheimer's disease (AD). mRNAs harvested from CSF samples will be used for analysis by an amplified antisense (aRNA) amplification methodology combined with cDNA array technology to provide an extensive, concurrent representation of hundreds of genes. Two specific aims are designed to refine a method for harvesting RNA from CSF and using this as a starting material for RNA amplification and hybridization to a variety of cDNA array platforms as outlined herein. Specific aim 1: Develop a novel method for reproducibly extracting and amplifying mRNA from CSF of two different populations of patients: subjects exposed to chemotherapy for the treatment of pediatric cancers and aged individuals with dementia. Specific aim 2: Combine the amplified RNA from Aim 1 with cDNA microarray technology to create expression profiles using CSF samples for molecular diagnosis of dementia and follow up of cognitive performance in long-term survivors of pediatric cancers by correlating cognitive status with rnRNA expression for a CSF-specific molecular fingerprint.